This invention relates to a method of manufacturing a member for use in a tire, particularly a reinforcing member superior in anti-cutting property and having an elongation not affecting tire performances.
Rubber members having wires embedded therein have been widely used as elastic members having anti-cutting property for various purposes. In a case that such rubber members are used as reinforcing members for products such as tires subjected to various external forces, wires embedded in the members are required to have elongations to an extent that do not detrimentally affect tire performance.
It has been proposed to permanently set wires in wave shapes to be embedded in rubber members. Such rubber members have been used as reinforcing members whose producing method has already been disclosed in Japanese Patent Application Laid-open No. 52-8,084.
Such a method of the prior art will be explained by referring to FIG. 1.
In the example of the prior art, filament wires 01 are used, which are wound about bobbins 02 rotatably supported and paid out thereof toward a guide plate 03.
The guide plate 03 is formed with a number of small apertures arranged in three rows vertically spaced from each other. In each row, the apertures are equally spaced. The wires 01 pass through the apertures in each of rows so as to be arranged in a plane. The wires 01 are then introduced between a pair of gear rollers 04.
The wires 01 in the three rows guided by the gear rollers 04 are alternately combined into a single plane and forced between the pair of gear rollers 04 into wave-shaped wires in vertical planes thereby changed from straight wires.
Thereafter, the wave-shaped wires pass between flat or smooth cylindrical rollers 05 so that the waves of the wires in the vertical planes will fall down into a horizontal plane to become two dimensional horizontal waves. The wires formed in horizontal waves are then fed into an extruder 06. The wires are coated with a rubber on their upper and lower sides and extruded from the extruder 06 to form a rubber member 07.
The series of processes above described are performed by pulling the rubber member 07 having the wire 01 embedded therein on an exhaust side of the extruder 06.
In these processes, if all the plurality of wires 01 do not have constant tensile forces immediately before entering between the gear rollers 04, stable permanent sets or deformations in wave shapes could not be accomplished, resulting in irregular waves of wires with high probability.
In the prior art, it is not clear that the bobbins 02 for winding the wires 01 thereon have brake means. Even if they have such means, it is very difficult to maintain equal tensile forces in all the wires 01 between the plurality of bobbins 02 and the gear rollers 04.
Therefore, it is difficult to obtain uniform waves of wires by means of the gear rollers 04. Rubber members 07 formed to include such non-uniform waves would have locally different extending forces so that they could not exhibit sufficient effect expected as reinforcing members.
Moreover, although the guide plate 03 is arranged upstream of the gear roller 04 to arrange the wires 01 in order, there is a tendency of the wires to be disturbed more or less immediately before entering between the gear rollers 04. Thus, positional relations between the wires 01 are apt to become unequal.
This is acute in the case where wires 01 are stranded wires. Such disturbances result from displacements of the wires caused by jerking action of the gear rollers at the moment when the wires enter between the gear rollers because of the absence of any regulating means immediately before the gear rollers.
Sinusoidal waves are the most preferable as the waveforms to be set in the wires because of their minimum decrease in tensile strength. In order to obtain waveforms similar to the sinusoidal waves it is needed to positively rotatively drive the pair of gear rollers 04 at the equal speeds to positively form the waves. In the prior art, however, the upper and lower gear rollers 04 are in general driven by the wires being pulled in downstream directions for shaping the wires into the waveforms. Therefore, the upper and lower gear rollers 04 do not necessarily rotate at equal speeds and teeth of the upper and lower gear rollers 04 do not maintain their predetermined positional relationship. Accordingly, crests of the waves formed in the wires are shifted onto either the upstream or downstream side as shown in FIG. 2.